Doctors will soon begin prescribing a new nicotine device that can help people stay off cigarettes for good

Smoking is complex. Just ask the 50 million Americans who continue to do it despite abundant evidence that as a diversion its safety ranks somewhere between bungee jumping and Russian roulette. For the past decade, addiction researchers have struggled to sort through the tangle of biological urges and psychological cravings that stir people to light up, in an attempt to develop better ways to kick the habit. That effort is finally beginning to bear fruit.

Over the next few months, four drug companies will introduce similar versions of the transdermal nicotine patch, a palm-size circular envelope that, when applied to the...